Change radio button in package header editor to a label.

Change radio button in package header editor to a label.
Force user to select GUID type when adding a GUID declaration.
Check duplicated PCD cName and toke value when adding a PCD declaration.
Change PCD token space text field to a drop-down list containing GUIDs with "TOKEN_SPACE_GUID" type and without type specified from GUID declarations in this package.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@1355 6f19259b-4bc3-4df7-8a09-765794883524